In the manufacture of cans for use as containers, such as beverage containers and particularly when the cans are formed from aluminum, the manufacturing processes generally employed produce a can body which at one stage has a longitudinal length greater than that desired for future operations to form a finished can body ready to receive an end cap and an uneven edge. Therefore, it is necessary that a portion of the sidewall of the can body be removed so as to produce a can body having a proper axial length. The most conventional methods for trimming a portion of the can body utilize knives or cutting edge in various ways in which there is relative rotation between the can body and the cutting edge. One such method is disclosed in U.S. Pat. No. 3,425,251 to Maytag wherein a can body is positioned over a rotatable upper knife and a large rotatable tool carrier wheel which has a knife mounted on a portion of its periphery so that during rotation of the tool carrier wheel the knife cooperates with the upper knife to trim away a portion of the can body. Maytag also discloses apparatus to cut and knurl the trimmed away portion of the can body. Another method for trimming a can body is disclosed in U.S. Pat. No. Re. 30,746 to Stroobants et al. wherein a turret is mounted on a rotatable main support shaft for rotation therewith and a plurality of cutter cartridge units are removably secured to the turret. During rotation of the turret, an untrimmed can body is positioned over a rotatable first knife which has a diameter substantially less than the inner diameter of the can body. A rotatable second knife is located so that it can be moved to a position to cooperate with the first knife to trim away a portion of the can body. The second knife has a diameter substantially less than the outer diameter of the can body. Stroobants et al. do not disclose an apparatus for cutting and knurling the trimmed away portion of the can body.
In the normal operation of a can body manufacturing operation using apparatus such as the type illustrated in U.S. Pat. No. 3,425.251 to Maytag, it is necessary to change the forming sleeve on the front end of the ram at periodic intervals because of wear and tear on the forming sleeve. At each change, the forming sleeve is reground and polished so that the diameter of the forming sleeve is reduced at each change. This of course results in the formation of can bodies having cylindrical sidewalls with smaller inner diameters after each change of the forming sleeve. In one type of operation, it is customary to change the forming sleeve between fifty and sixty times, so that can bodies of fifty to sixty differing diameters are produced. This also has an effect on the apparatus wherein a portion of the can body having an uneven edge at the open end thereof is trimmed away. In such apparatus, it is conventional to use a collapsible mandrel wherein a plurality of resilient fingers are integral with a support having a longitudinal axis wherein the resilient fingers extend in axial and radially outward directions from the support. A locking ring is used in conjunction with the support and the resilient fingers to limit the radially outward movement of the resilient fingers while permitting limited radially inward movement of the resilient fingers. The resilient fingers are designed to contact the inner peripheral surface of the can body so as to hold the can body for rotation therewith. The nature of the resilient fingers is such that when the diameter of the inner peripheral surface has been changed by several changes of the forming sleeve, it is necessary to change the locking ring because either too much force has to be placed on the can bodies to move the can bodies over the resilient fingers having an outer diameter for can bodies having larger inner diameters or the resilient fingers will not hold the can body firm enough to prevent relative rotation between the can body and the resilient fingers. Thus, as described below, even though the difference in inner diameters of the can bodies and outer diameters of the resilient fingers as controlled by the locking rings is very small, it is necessary to change the locking rings for can bodies of smaller or larger inner diameters for the satisfactory operation of the can body trimming apparatus. In trimming apparatus used with the can body manufacturing apparatus described above, it is customary to have six different locking rings to accommodate the fifty to sixty differing sizes of can bodies. The forming sleeves for the above operation have a maximum diameter of 2.4783 inches and a minimum diameter of 2,4723 inches and the six locking rings have internal cylindrical surfaces for limiting the radially outward movement of the resilient fingers having diameters of 2.007; 2.009; 2.011; 2.013; 2.015 and 2.017 inches. Therefore, after a plurality of changes of the forming sleeves, it is necessary to change the locking ring of the trimming apparatus. In some trimming apparatuses, a plurality of trimming stations are mounted on a rotating turret so that, when can bodies having a different internal diameter are to be processed, it is necessary to change a plurality of locking rings.